Prior to the present invention, various systems have been devised to improve the performance of internal combustion engines and more particularly diesel engines by controlling fuel intake and subsequent pumping of the fuel into the combustion chambers of the engines through their injectors.
Generally, prior systems and controls for controlling the injection event have featured the ending of the event by (1) gradually decaying injection pressure as the pumping plungers slow down going over the nose of the pumping ramp of an associated cam, or (2) by rapidly terminating injection pressure with sharp cut off by opening a fuel feed port mechanically or electrically. However, such controls produce high emissions when the engine runs at high speed and there is a gradual decay in injection pressure as in (1) above. Further, high emissions and also noise levels occur at low engine speeds including idle when there is a sharp cut off in injection pressure as in (2) above. Such prior systems offered either a sharp ending injection rate or a soft ending injection rate with the cam velocity profile chosen to be the best compromise profile for overall engine performance. To provide for improved injections, various constructions and methods have been devised which include electronically controlled injection. An example of such system is disclosed is U.S. Pat. No. 4,757,795, issued Jul. 19, 1988 to William Kelly, in which a solenoid valve is employed to meter quantities of fuel into the combustion chambers. However, to meet new and higher standards for emission, noise and economy, new and improved fuel injection control systems and injection methods are required. To this end, the present invention meets such requirements by straight forward controls and methods by which the rate of fuel injection and profiled of the fuel pulse waves can be varied to optimize engine performance for all engine speeds and loads.